Vocab Lesson 5

4. a person who make sure the players are following the rules
7. a change in the genes that causes it to become different from others
8. the ability to do something for a long time
9. to put substance into a person's body
11. A part of cell that influences growth
12. the treatment of physical problem or illness
15. the degree to which something is thick or heavy
16. a good position or condition that helps to make someone or something better

1. a person who plays sports
2. to improve the quality, amount or strength of something
3. difficult to understand
5. to change something to improve it
6. a medical condition which makes the patient feel very thirsty
10. to put something in the place of something
13. to make something last
14. great physical or mental strength that allows you to endure for long time